What happened
On June 22, 2002, at approximately 13:30 local time, a Robinson R-22 Beta helicopter, registration EC-FEX, crashed into the water of the Canelles Reservoir in the municipality of Os de Balaguer, Lérida. The aircraft was conducting a private VFR flight, having picked up a passenger from Benabarre for a recreational trip.
While flying near the Canelles Dam, the pilot identified electrical power lines spanning the area. In an attempt to climb over these cables, the pilot applied significant collective input. During this maneuver, the helicopter experienced a sudden loss of altitude. To avoid striking the wires, the pilot instinctively lowered the collective and pulled the cyclic, but the aircraft entered an uncontrolled descent. The helicopter struck the water in a drainage basin of the dam, resulting in one fatality (the passenger) and one serious injury (the pilot).
The investigation
The CIAIAC investigation focused on the aerodynamic performance of the aircraft during the maneuver and the pilot's control inputs. Investigators examined the aircraft's maintenance records, which showed the engine and airframe were in compliance with all required inspections. The investigation also analyzed the physical evidence at the impact site, noting that the impact occurred in a basin approximately 5 meters deep.
Technical analysis revealed that the engine was functioning normally and there was no evidence of mechanical failure. Instead, the investigation established that the primary issue was a significant drop in the main rotor's RPM. The investigation also considered the low inertia of the R-22 rotor system, which makes it highly sensitive to rapid changes in collective pitch.
Findings
- The primary cause of the accident was a decrease in main rotor RPM during an ascent intended to clear electrical power lines near the dam.
- The pilot was unable to recover the lost rotor RPM during the subsequent uncontrolled descent.
- The loss of RPM was triggered by an excessive power demand caused by the pilot's attempt to climb over the obstacles.
- The pilot's instinctive reaction to pull the cyclic during the descent likely increased the blade angle of attack, further hindering the recovery of rotor speed.
- The low inertia of the R-22 rotor system contributed to the rapid decay of rotor speed following the sudden collective input.